In FY 2015, we continued our investigation of virulence factors that contribute to Staphylococcus aureus pathogenesis and immune evasion. The focus is on understanding which factors define the virulence potential of highly virulent MSSA and MRSA clones, in particular of community-associated MRSA. For example, we analyzed the virulence factors contributing to an emerging, highly virulent MSSA clone that caused several cases of fatal pneumonia in Brazil. Furthermore, we continued our close and fruitful collaboration with Dr. Min Li in Shanghai, analyzing several virulence factors of CA-MRSA and hospital-associated MRSA clones that are predominant in China. Finally, we continue our mechanistic studies on phenol-soluble modulins, peptide toxins of S. aureus identified in our laboratory.